The invention relates to polymer compositions.
Polymer compositions that include polar polymers and olefinic polymers are known. These polymer compositions often include one or more additional compounds which act as compatibilizers for the polar and olefinic polymers.
The invention relates to polymer compositions. These compositions can exhibit good flame retardancy and/or low smoke formation. The polymer compositions can provide good mechanical properties, such as tensile strength and elongation. The polymer compositions can contain small amounts of halogens. The compositions can be in the form of a blend.
In one aspect, the invention features a polymer blend that includes an olefinic polymer, a polar polymer and an additional polymer that includes first and second polymer portions. The first polymer portion is compatible with the olefinic polymer, and the second polymer portion is compatible with the polar polymer.
In another aspect, the invention features a method of making a polymer composition. The method includes forming a polymer comprising first and second polymer portions in a mixture. The mixture includes an olefinic polymer and a polar polymer. The first polymer portion is compatible with the olefinic polymer, and the second polymer portion is compatible with the polar polymer.
In another aspect, the invention features a method of forming a polymer composition. The method includes forming a polymer containing first and second polymer portions, and mixing the polymer in a mixture. The mixture includes an olefinic polymer and a polar polymer. The first polymer portion is compatible with the olefinic polymer, and the second polymer portion is compatible with the polar polymer.
The preferred compositions include an olefinic polymer, a polar polymer and a compatibilizer. The compatibilizer can be a block or graft copolymer. The compatibilizer includes at least one olefinic polymer portion that is compatible with the olefinic polymer, and the compatibilizer includes at least one polar polymer portion that is compatible with the polar polymer. The polymer portions can be in the form of blocks.
Typically, the compositions are in the form of a blend in which the components of the composition are intermixed. The blend can be a homogeneous blend.
Olefinic polymers are formed primarily of olefin monomers which are hydrocarbon monomers having at least one carbon-carbon double bond. Olefin monomers can be straight chained, branched or cyclic hydrocarbons. Examples of olefin monomers include ethylene, propylene, butylene and pentene. Examples of olefinic polymers include polyethylene, ethylene copolymers, polypropylene, propylene copolymers, ethylene propylene copolymers and polymethylpentene polymers.
In addition to olefin monomers, an olefinic polymer can include a minor amount of non-olefinic monomers, such as ethylene acrylic monomers. Preferably, an olefinic polymer includes less than about 20 weight percent non-olefinic monomers, more preferably less than about 10 weight percent non-olefinic monomers and most preferably less than about 5 weight percent non-olefinic monomers.
Preferably, an olefinic polymer includes at least about 80 weight percent olefin monomers, more preferably at least about 90 weight percent olefin monomers, and most preferably at least about 95 weight percent olefin monomers.
Olefinic polymers preferably include less than about 2 weight percent halogen, more preferably less than about 1 weight percent halogen and most preferably less than about 0.5 weight percent halogen.
Olefinic polymers are available from, for example, Exxon, Mobil, Chevron, Amoco, Dow, Quantum, Solvay, Novacor, Rexene, Aristech, Hoechst Celanese, Fina, Montall and Shell.
A polar polymer includes olefin monomers and polar monomers having the formula CH2=CHOCOR, where R is a hydrocarbon group that can be straight chained or branched, saturated or unsaturated, and substituted or unsubstituted. Typically, R is a straight chained, saturated and unsubstituted alkyl group having from one to five carbon atoms, such as a methyl group, an ethyl group or a butyl group. In a polar polymer, a portion of the polar monomers can be hydrolyzed.
A polar polymer can include additional functional monomers such as carbon monoxide, acrylic monomers, glycidyl acrylic monomers, acid monomers, anhydride monomers, and/or nitrile monomers.
Preferably, a polar polymer includes from about 20 weight percent to about 90 weight percent olefinic monomers, more preferably from about 35 weight percent to about 85 weight percent olefinic monomers, and most preferably from about 50 weight percent to about 80 weight percent olefinic monomers.
Preferably, a polar polymer includes from about 10 weight percent to about 80 weight percent polar monomers, more preferably from about 15 weight percent to about 65 weight percent polar monomers, and most preferably from about 20 weight percent to about 50 weight percent polar monomers.
Preferably, a polar polymer includes at most about 15 weight percent additional functional monomers, more preferably from about 2.5 weight percent to about 10 weight percent additional functional monomers.
Polar polymers preferably include less than about 2 weight percent halogen, more preferably less than about 1 weight percent halogen, and most preferably less than about 0.5 weight percent halogen.
In a preferred embodiment, the polar polymer is a terpolymer of ethylene monomers, vinyl acetate monomers and carbon monoxide.
Polar polymers are available from, for example, Exxon,.Quantum, DuPont, Union Carbide, AT Plastics, Chevron, Bayer, Mitsubishi Petrochemicals and Sumitomo.
The compatibilizer is typically a graft or block copolymer that includes at least one olefinic polymer portion and at least one polar polymer portion. The polymer portions can be in the form of blocks.
The olefinic polymer portion is formed of an olefinic polymer, and the polar polymer portion is formed of a polar polymer. The olefinic polymer portion should be selected to be compatible with the olefinic polymer, and the polar polymer portion should be selected to be compatible with the polar polymer. Generally, the olefinic polymer portion of the compatibilizer and the olefinic polymer have substantially the same polarity, and the polar polymer portion of the compatibilizer and the polar polymer have substantially the same polarity.
Preferably, the olefinic polymer portion of the compatibilizer is the same polymer as the olefinic polymer. For example, if the olefinic polymer is polyethylene, the olefinic polymer portion of the compatibilizer is also polyethylene.
Preferably, the polar polymer portion of the compatibilizer includes functional groups that are the same as the functional groups in the polar polymer. For example, if the polar polymer is ethylene vinyl acetate, the polar polymer portion of the compatibilizer includes vinyl acetate monomers.
The polymer compositions can include from about 15 weight percent to about 65 weight percent olefinic polymer, from about 20 weight percent to about 80 weight percent polar polymer, and from about 1 weight percent to about 40 weight percent compatibilizer.
The olefinic polymer portions and polar polymer portions of the compatibilizer can be directly chemically bonded or they can be connected by a linking agent that is chemically bonded to an olefinic polymer portion and an adjacent polar polymer portion.
When a linking agent is not used, the compatibilizer can be formed by reacting two polymers that contain functional groups that react to provide the compatibilizer. This reaction can occur in a mixture that contains the olefinic polymer and the polar polymer. Alternatively, the compatibilizer can first be formed then added to a mixture that contains the olefinic polymer and the polar polymer.
An amine and/or epoxy containing polymer, such as a nitrile rubber, can be reacted with an acid or anhydride containing polyolefin. An acid or anhydride containing polymer, such as a nitrile rubber, can be reacted with an amine and/or epoxy containing polyolefin. An isocyanate containing polyester (typically having a low molecular weight) can be reacted with an acid, anhydride or epoxy containing polyolefin. A compatibilizer can be formed by reacting an epoxy containing terpolymer of ethylene, vinyl acetate and carbon monoxide with a maleic acid modified polypropylene. A compatibilizer can be formed by reacting an ethylene methyl acrylate acid containing polar polymer with an epoxy containing styrene ethylene butylene styrene block copolymer.
Preferably, the functional groups that react to form the compatibilizer are at the terminus of the polymers.
Examples of linking agents include diepoxides, diamines and diisocyanates which can be reacted with an acid modified polar polymer and an acid modified olefinic polymer to provide a compatibilizer.
The polymer compositions can be prepared using standard mixing methods. For example, the polymer compositions can be formed using a Banbury mixer, a Brabender mixer and/or a twin screw mixer. Generally, twin screw mixers provide a higher shear during mixing, so polymer compositions formed using a twin screw extruder can exhibit better elongation and tensile properties.
The polymer compositions can also include compounds that improve the hydrolytic stability of esters, silicones, stabilizers, flame retardants, plasticizers, colorants, reinforcing fillers and/or lubricants. Preferably, the total amount of these compounds in the polymer compositions is from about 50 to about 200 parts per 100 parts of total amount of polymer (olefinic polymer, polar polymer and compatibilizer). When the composition includes anti-oxidants or lubricants, these compounds make up from about 100 parts per million to about 10 weight percent of the composition relative to the total amount of polymer (olefinic polymer, polar polymer and compatibilizer).
Examples of compounds that improve the stability of esters include polycarbodiimides, such as aromatic polycarbodiumides. These compounds are available from, for example, Bayer.
Examples of colorants include organic and inorganic colorants. Colorants are available from, for example, Ciba Geigy, BASF, Ferro, ICI, Harwick and Teknor Apex.
Examples of flame retardants include aluminum trihydrate, magnesium hydroxide, phosphorus compounds, nitrogen compounds, zinc borates, halogenated compounds, and Ultracarb (Microfine Minerals). Flame retardants are available from, for example, Lonza, Alcoa, Alcan, Huber, Martin Marietta, Hoechst Celanese, U.S. Borax, Melamine Chemicals, Microfine Minerals and Anzon.
Examples of stabilizers include heat stabilizers, metal deactivators and ultraviolet stabilizers. Stabilizers are available from, for example, Ciba Geigy, Sandoz, Cytec, Eastman Chemicals, Fairmount Chemicals, Hoechst Celanese and General Electric.
Examples of plasticizers include phosphate ester plasticizers, phosphoric esters, fatty acid esters, esters of azelaic acid, esters of sebacic acid, trimellitic esters and polymeric plasticizers. When the polymer compositions are used in flame retardant applications, phosphate ester plasticizers are preferably used. Plasticizers are available from, for example, Solutia, Teknor Apex, Ferro, Exxon, Eastman Chemical and Uniflex Chemical.
Lubricants are available from, for example, Akzo, Dow Corning, DuPont, Astor Wax, Henkel, Witco and Struktol.
Silicones are available from, for example, General Electric, Wacker silicones and Dow Corning.
Examples of reinforcing fillers include clay, silica and calcium carbonate. Reinforcing fillers are available from, for example, Haber, Engelhard and PPG.
The polymer compositions preferably have an elongation of at least about 100% as measured according to ASTM D-638.
The polymer compositions preferably have a tensile strength of at least about 1000 as measured according to ASTM D-638.
The polymer compositions preferably have a peak smoke rating of less than 3/meter as measured using cone calorimetry according to ASTM E-1354.
When used for flame retardant applications, the polymer compositions preferably have a limiting oxygen index of at least about 30 as measured by ASTM D-2863.